The present invention relates to pumping systems for ultra-high and extreme high vacuum applications, and more particularly to backing up pumps for turbomolecular pumps in such applications.
Recent technological advances in wide range turbopumps make them very attractive for ultra-high and extreme high vacuum applications. The major deterrent to the use of such pumps is the need for a backing up pump (such as a diaphragm pump) as a roughing pump. Extended operation of a wide range turbopump without a backing pump has been demonstrated by Weber et al., JVST A 14(5) 2695-2698. According to this work, such operation was accomplished in a 13 liter volume that was initially evacuated with a sorption pump and then valved off. In such an arrangement, the principal difficulty is achieving a low partial pressure of hydrogen due to the tendency of hydrogen to adsorb to the walls of most volume containers. The use of a sputter-ion pump has also been suggested and demonstrated as an alternative backing pump in such applications.
It is therefore an object of the present invention to provide an alternative to a backing pump in the application of turbomolecular pumps in ultra-high and extra high vacuum applications.
According to the present invention, palladium oxide is used to convert hydrogen present in the evacuation stream and related volumes to water with the water then being cryo-pumped to a low pressure of below about 1.exe2x88x925 Torr at 150xc2x0 K. Cryo-pumping is achieved using a low cost Kleemenco cycle cryocooler or a somewhat more expensive thermoelectric cooler such as a Peltier cooler. Such a system serves as a relatively low cost, yet highly efficient substitute for the previously described prior art apparatus.